the economist Adam Smith took on board the doctors’ discovery that meat was a superfluous luxury and this provided an important cog in the taxation system of his seminal treatise on the free market. (p. xxiv)

More interestingly,

As environmental degradation and population growth became serious problems in Europe, economists turned to the pressing question of limited natural resources. Many realised that producing meat was a hugely inefficient process in which nine-tenths of the resources pumped into the animal were wastefully transformed into feces. (p. xxv)

And this has nothing to do with economists (be grateful), but

The poet Percy Bysshe Shelley joined an eccentric network of nudist vegetarians who were agitating for social revolution. (p. xxv)